1. Field of the Invention
The present invention relates to a management apparatus and management method for a water-based resist stripping liquid used in the stripping of resists in a semiconductor manufacturing process or the like.
2. Description of the Related Art
A resist material used in a photolithography step in a semiconductor manufacturing process or a flat panel display substrate manufacturing process maybe a positive type that becomes soluble upon exposure to light or a negative type that becomes insoluble upon exposure to light, although it is the positive type that is used predominantly. A typical example of a positive type resist has as principle components thereof a naphthoquinone diazido type photosensitizer and an alkali-soluble resin (novolac resin).
In the final stage of the photolithography step, it is necessary to completely strip the resist from the substrate. This resist stripping process for a semiconductor or a flat panel display substrate includes both a dry ashing step using an oxygen plasma and a wet stripping step using a resist stripping liquid. During the dry ashing step using the oxygen plasma, silicon oxide and/or aluminum oxide is produced on the substrate, and hence in the subsequent wet stripping step it is necessary not only to strip the resist but also to completely remove such metal oxides.
Regarding the above, Japanese Patent Application Laid-open No. 7-235487 discloses a resist stripping liquid management apparatus that comprises resist stripping liquid discharge means that detects the concentration of resist dissolved in a resist stripping liquid using an absorption photometer and discharges the resist stripping liquid, first replenishing means that detects the liquid surface level of the resist stripping liquid using a liquid surface level gauge and replenishes with organic solvent and ailcanolainine, or replenishes with resist stripping new liquid in which the organic solvent and the alkanolamine have been premixed, and second replenishing means that detects the concentration of the alkanolamine in the resist stripping liquid and replenishes with at least one of the organic solvent and the alkanolamine.
Moreover, Japanese Patent Application Laid-open No. 10-22261 discloses a resist stripping liquid management apparatus that comprises resist stripping liquid discharge means that detects the concentration of resist dissolved in a resist stripping liquid using an absorption photometer and discharges the resist stripping liquid, first replenishing means that detects the liquid surface level of the resist stripping liquid using a liquid surface level gauge and replenishes with resist stripping stock liquid and pure water or replenishes with resist stripping new liquid in which the resist stripping stock liquid and pure water have been premixed, and second replenishing means that detects the water concentration in the resist stripping liquid using an absorption photometer and replenishes with at least one of the resist stripping stock liquid and pure water.
In the resist stripping process for a semiconductor or a flat panel display substrate, it is common to use a solution containing an organic alkali or an organic solvent as the resist stripping liquid, and it has become clear that such a solution to which a suitable amount of water has been added exhibits excellent effects. Specifically, with a resist stripping liquid containing a suitable amount of water (water-based resist stripping liquid), it is possible to reduce the substrate treatment temperature from about 80° C. to about 40° C., and thus alleviate undesirable effects on the metal that forms the foundation of the substrate or semiconductor circuit. Moreover, a water-based resist stripping liquid has advantages such as being handleable as a noncombustible material, having high stability, loss due to evaporation being predominantly that of water, which is inexpensive, and the resist stripping rate being high.
Examples of such a water-based resist stripping liquid include a mixed solution of a dimethylsulfoxide and pure water, a mixed solution of an N-methylpyrrolidone derivative and pure water, and a mixed solution of an alkanolamine, glycol ether and pure water. These water-based resist stripping liquids are used with a spraying method, a dipping method or the like.